Synthesis of Activated Biochar from the Bark of Moringa oleifera for Adsorption of the Drug Metronidazole Present in Aqueous Medium

Moringa oleifera seeds, in particular, have been used for water and wastewater treatment due to their ability to remove many pollutants. Therefore, the present work aims to produce bioadsorbent materials by pyrolysis using biomass from the seed shell of Moringa oleifera to remove the drug Metronidazole present in an aqueous medium. The biochars produced were activated with phosphoric acid (H3PO4) and potassium hydroxide (KOH) to compare the material’s modifications and adsorption mechanisms with the biochar in nature (BCM). The biochars were characterized by Point-of-zero charges (pHpzc), Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The studies showed that the adsorption behavior varied with the pH of the solution. The adsorption study verified that the activated biochars presented better results, so in the kinetic study, the adsorption behavior occurred rapidly in the initial minutes until stabilizing within 3–4 h, better fitting the Elovich model. Isotherm models were tested, where the experimental data were adjusted to the Sips model, with an adsorption capacity of 18 mg g−1 for acid-activated biochar (BCH3PO4) and KOH-activated biochar (BCKOH) with 366.49 mg g−1. The results showed that biochars, especially BCKOH, become viable for production because they are a low-cost material and highly effective in removing drugs.